The present invention relates to a pump, and more particularly to a diaphragm pump.
As a general rule, a conventional pump comprises a body having a bottom portion for communicating with a dip tube via an admission valve and a top portion for connection to the edge of a container and itself containing a metering chamber closed in leaktight manner on top by compression means provided with an exhaust valve and with a return member, and suitable for being actuated by manual thrust being applied to a dispenser head provided with a delivery duct.
Unfortunately, those pumps require a metal spring to be used for returning the compression means into the high position, and they also require admission and exhaust valves of complex configurations to be made using other metal elements such as balls.
Consequently, those pumps are made up of numerous parts made of various materials so that fabrication and assembly costs are penalizing.
An object of the invention is to solve those technical problems for simplification and cost-reducing purposes, but without compromising the reliability and accuracy qualities of the pump.
In the pump of the invention, said return member comprises an elastically deformable internal diaphragm carried by the dispenser head and co-operating with a rigid cup fixed beneath said head and defining with said diaphragm the metering chamber.
EP-A-0 452 260 discloses a pump having a diaphragm which acts as a return member. The diaphragm covers a rigid cup which defines the bottom of the metering chamber. The dip tube is integral with said rigid cup, a valve being fastened on the top opening of said tube. A plate, fixed under the diaphragm, is in register with the bottom of the chamber.
EP-A-0 951 944 also discloses a pump having a diaphragm which acts as a return member. A tubular element fixed to said diaphragm includes a top portion which extends into the metering chamber and which carries the admission valve at its end, and a bottom portion which is fixed around the dip tube, under the bottom wall of the metering chamber.
The invention seeks to simplify the pump further, without compromising its reliability and accuracy qualities and by reducing the internal volume of the metering chamber when thrust is applied to the dispenser head.
According to the invention, to achieve this object said diaphragm in the free state is of U-shaped section and has a cylindrical socket mounted coaxially and in leaktight manner around the top portion of the dip tube which projects into the metering chamber.
According to an advantageous characteristic, said diaphragm has at least one feed orifice associated with a central solid disk suitable for being pressed in leaktight manner against the top orifice of the dip tube so as to form an admission valve.
In a variant embodiment, the central solid disk is connected to said diaphragm by three radial bridges defining three feed orifices between one another.
According to another characteristic, said rigid cup has a central delivery channel opening out into the delivery duct of the dispenser head via said exhaust valve.
In a specific variant, the bottom edge of said rigid cup is formed with a peripheral collar for bearing in deforming manner against said diaphragm.
According to yet another characteristic, said cup is received at least in part inside said diaphragm.
Preferably, the free edge of said diaphragm is held captive by said cup inside the dispenser head.
According to yet other characteristics, the outside wall of said diaphragm has a peripheral rib serving both to position the bottom edge of the dispenser head and to slide freely relative to the inside wall of the body.
In another specific embodiment, said exhaust valve is constituted by a flexible tongue carried transversely by the bottom end of the delivery duct of the dispenser head.
The pump of the invention presents a structure that is very simple without any metal element.
Only three parts are thus capable of performing the essential functions of the pump.
These parts are made by molding a plastic material and/or an elastomer material and they can be assembled together easily, quickly, and automatically.